1. Field of the Invention
The present invention relates to a pen input and output (I/O) unit for inputting data by touching or contacting an input surface of a tablet device with a pen (stylus) and for displaying the input data on a display device.
2. Related Art
A pen I/O unit such as a pen computer using, as an input device, a tablet device in which a tablet and a display device are integrated, and a pen cooperated with the tablet device, has been known. In such a pen computer, when a desired numeric value is input, it is often performed that a numeric value displayed on the display device is counted up or down with a predetermined input operation to obtain the desired value. As the predetermined input operation, two major methods are used. In the first method, an operator repetitively touches an input area of the tablet device with the pen a predetermined number of times. The number of the contacts are counted and the counted value is input to a central processing unit (CPU). In the second method, displayed data is continuously updated depending on a time period during which the pen is continuously in contact with the input area.
However, in the first method, the pen must repetitively be contacted to the input surface of the tablet device. Fine wiring patterns in the tablet, the display device and the pen are liable to break due to mechanical shocks caused by the contact. Further, the input operation is troublesome, and the sound caused by the pen contacting with the tablet is harsh.
In the second method, when a speed of updating the displayed value is too fast, the desired value may be surpassed. In order to correct the displayed value, a further update operation in a reverse direction is required. Accordingly, it is difficult to obtain the desired value at once. On the contrary, when a speed of updating the displayed value is too slow, it is time-consuming to get a desired value.